Some years ago, I was a bit mystified as to the distinction
between prebiotics and probiotics.

These days, one can easily look them up on
Wikipedia, and find that prebiotics are meant to
encourage the growth of ‘good’ bacteria in the gut, while probiotics are supposed
to deliver the bacteria directly.

Prebiotics are generally soluble oligo- or
polysaccharides, known as dietary ‘fibre’, and one of the best sources of these
is chicory root.

Chicory root and
flower

The history of probiotics starts back in the
19th century with the work of Ilya Ilyich
Mechnikov, who received the 1908
Nobel Prize in Physiology or Medicine for his discovery of phagocytes, along with
Paul
Ehrlich (treatment of syphilis). Mechnikov’s theory, that certain white
blood cells could engulf and destroy harmful bodies such as bacteria, met with
scepticism from leading specialists including Louis Pasteur, Emil Adolf von
Behring and others. At the time most bacteriologists believed that white
blood cells ingested pathogens and then spread them further through the
body.

Mechnikov also developed a theory that aging is caused by toxic
bacteria in the gut and that lactic acid could
prolong life. Based on this theory, he drank sour milk every day. His book
The Prolongation of Life: Optimistic Studies, along with his studies into
the potential life-lengthening properties of lactic acid bacteria, inspired
Japanese scientist Minoru Shirota to
begin investigating the causal relationship between bacteria and good intestinal
health, eventually leading to the development of a bacterial strain
Lactobacillus casei strain shirota which from 1935 is the basis of
Yakult
(ヤクルト the Japanese name
based on ‘yoghurt’: 养乐多 or 益力多 ‘benefit happiness/strength a
lot’, depending on where you are in China.)

But
— the big question — do the ‘good’ bacteria actually reach the gut? In order to
reach the intestine, where they are needed, they have to pass the stomach with
its very acidic gastric juice. Microencapsulation is widely used these days for
delivering drugs (and lots of other things) so why not bacteria? There has
been, much work on this, reviewed in The Gut Microbiota and
Human Health with an Emphasis on the Use of Microencapsulated Bacterial
Cells [1], which includes a Table of
types of microcapsules available for the targeted delivery of probiotic
bacteria.

Three references there are given to complex capsules made of
the two polymers alginate and chitosan, however there is some more recent
research into developing multilayer systems. Again, the two main polymers are
the same, namely Alginate, derived from
seaweed, and Chitosan, derived from
crustacean shells.

Alginate

Chitosan

Although these are both polysaccharides, they
have significantly different properties which allow them to work better in
harmony when passing through the stomach. Alginate is in general a very good
encapsulator, but it does not protect the microbes sufficiently from gastric
juice. Chitosan, at first sight, seems to labour under two disadvantages. It
is a known antimicrobial agent and is yet is degraded by microbial action,
especially by the enzyme chitosanase. (Paradox? Maybe one is the solid form,
the other in solution). However, if the inner layer of the capsule is alginate,
chitosan is very slow to diffuse in to the microbes, while chitosan ionically
bound to the alginate is attacked much more slowly by the enzyme.

Bifidobacterium breve is commonly offered as a
probiotic supplement. The Wikipedia article
deals with the whole Bifidobacterium genus as a whole, but searching for
B. breve yields many results from people marketing probiotic
products, and as sources of information they might be biased, and generically
overlooking the problem of travel through the stomach. I doubt, though, if we
will see encapsulated bugs in ‘foodie’ products any day soon. But where someone
has a clinical condition involving imbalance of the intestinal microflora, this
might turn out to be a useful method of delivery.

So does this mean that
there is no point in consuming Yakult? That would depend on how directly the
bacteria were exposed to stomach fluid. The advice from one of the authors is
that the bacteria are most vulnerable when the stomach is empty and the pH is
low. So if you like Yakult, take it with
meals.

Comments

Mechnikov also developed a theory that aging is caused by toxic bacteria in the gut and that lactic acid could prolong life. Based on this theory, he drank sour milk every day. His book The Prolongation of Life: Optimistic Studies, along with his studies into the potential life-lengthening properties of lactic acid bacteria, inspired Japanese scientist Minoru Shirota to begin investigating the causal relationship between bacteria and good intestinal health, eventually leading to the development of a bacterial strain Lactobacillus caseistrain shirota which from 1935 is the basis of Yakult

'Mechnikov died in 1916 in Paris from heart failure'. Whoops, maybe he overlooked a few other important aspects of health and longevity? Interesting article Robert :)

Prebiotics are generally soluble oligo- or polysaccharides, known as dietary ‘fibre’, and one of the best sources of these is chicory root.

Chicory roots are about 8% inulin(fiber). The source also reports that when roasted, inulin converts to oxymethylfurfural, which is at least partly responsible for the coffee-like smell.It's an old nomenclature that neither I nor chemspider recognize. In any case in regular coffee, furfurals are not responsible for any of the typical aromas. But I digress...!

In any case in regular coffee, furfurals are not responsible in any of the typical aromas. But I digress...!

Interesting digression though Enrico, trying to understand what is responsible for coffee's typical aromas and why doesn't it taste as good as it smells?i The article you linked to says that :-

Coffee aroma is responsible for all coffee flavor attributes other than the mouthfeel and sweet, salt, bitter, and sour taste attributes that are perceived by the tongue. Therefore, it might be said that coffee aroma is the most important attribute to specialty coffee. Even instant coffee has the components responsible for stimulation of our taste buds. The difference, however, is that instant coffee lacks most of the aromatic volatile compounds causing a dramatic decrease in the overall coffee flavor....Coffee aroma is perceived by two different mechanisms. It can either be sensed nasally via smelling the coffee through the nose or retronasally. Retronasal perception occurs when the coffee is either present in the mouth or has been swallowed and aromatic volatile compounds drift upward into the nasal passage...

...The number of aromatic compounds found in coffee increases every year. Today the number is well over 800, and as our analytical methods become more precise, more will be uncovered. Yet, the perception of coffee aroma is dependent upon both the concentration of the compound and its odor threshold. With that said, understanding coffee aroma is not as difficult as understanding how over 800 coffee elements interact with the olfactory epithelium.

Recently resuming working full time again has one big drawback for me, apart from the loss of freedom to do more or less what I want when I want on those days and that is having to drink instant coffee again, after several years without it. Someone once showed me years ago, that if you mix the instant coffee powder with milk before adding the hot water, the coffee tastes much better than if you don't. I agree that it does seem to but why would that be I wonder, when coffee is originally made by roasting coffee beans in heat?